Nozzle for rotary piston engine

ABSTRACT

In a rotary piston engine, there is provided a system for purifying the exhaust gas to reduce NOx (nitrogen oxide) in the exhaust gas by recirculating the exhaust or combustion gas into an intake mixture or a system for purifying the exhaust gas to reduce unburned components such as CO, HC, etc. in the exhaust gas by supplying secondary air to the exhaust or combustion gas, and an outlet nozzle for the combustion gas or a supply nozzle for secondary air are adapted to open in the exhausting stroke chamber. Means are provided for preventing sludge from accumulating upon or adhering to the nozzles.

United States Patent 1 1 Shimizu 1451 Mar. 5, 1974 1 NOZZLE FOR ROTARYPISTON ENGINE [75] Inventor:

[73] Assignee: Toyo Kogyo Company Limited,

Hiroshima, Japan 1221 Filed: Dec. 22, 1971 211 App]. No; 210,949

{30] Foreign Application Priority Data Dec. 22, 1970 Japan 45-130358Dec. 22, 1970 45-130359 Dec. 23, 1970 45-130348 Dec. 23, 1970 Japan45-130349 [52] US. Cl. l23/8.0l, 123/845 [51] Int. Cl F02b 53/00 [58]Field of Search 123/8111, 8.13, 8.45, 119 A, 123/807 [56] ReferencesCited 7 UNITED STATES PATENTS 7 3,476,092 ll/l969 Yamamoto 123/8073,097,632 v 7/1963 Froedc et al 123/8.45 X

Hiroshi Shimizu, Hiroshima, Japan 7 3,168,078 2/1965 Camm 123/8133,546,878 12/1970 Yoshimurm. 123/845 X 3,464,394 9/196) Satoh [ZS/8.453,265,046 1 1/1966 Puschkc 123/813 Primary Examiner-Carlton R. CroylcAssistant ExaminerMichacl Koczo, Jr.

Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn & Macpeak [57]ABSTRACT In a rotary piston engine, there is provided a system forpurifying the exhaust gas to reduce NOx (nitrogen oxide) in the exhaustgas by recirculating the exhaust or combustion gas into an intakemixture or-a system for purifying the exhaust gas to reduce unburnedcomponents such as CO, HC, etc. in the exhaust gas by supplyingsecondary air to the exhaust or combustion gas, and an outlet nozzle forthe combustion gas or a supply nozzle for secondary air are adapted toopen in the exhausting stroke chamber. Means are provided for preventingsludge from accumulating upon or adhering to the nozzles.

20 Claims, 21 Drawing Figures PAIENTED 5 I974 saw 1 nrs BACKGROUND OFTHE INVENTION This invention relates to improvements in the structure ofa nozzle adapted to open in an exhausting stroke chamber of a rotarypiston engine.

Heretofore, there have been used means for reburning unburned componentssuch as CO, HC, etc. contained in the exhaust gas by supplying secondaryair for purifying the exhaust gas in an internal combustion engine, andin this method, since the unburned gas is reburned by the heat energy ofthe exhaust gas itself, it is known that the higher the temperature ofthe exhaust gas at the position where the'secondary air is supplied, themore effective oxidizing reaction is developed.

Therefore, in case of a rotary piston engine, it is preferable that thesupplying position of the secondary air is provided in the combustion orexhausting stroke chamber in which the temperature of the exhaust gas ishighest. The supplying positionmay be selected as being on the centerhousing or side housing forming the exhausting stroke chamber. However,if a supply nozzle for the secondary air is merely opened on the innersurface of the center or side housing, the nozzle will become loadedwith sludge since the seal is slidably in contact with the inner surfaceof the housing. Therefore, the nozzle becomes clogged and the secondaryair cannot be supplied in an extremely short time period. Accordingly,such a secondary air supplying device has not yet been put intopractical use ina rotary piston engine.

In order to remove NOx (nitrogen oxide) contained in the exhaust gasexhausted from the engine, it is known that part of combusion gas isrecirculated into the intake mixture to reduce the combustion efficiencyof the engine. When such an exhaust gas recirculating system is appliedto the rotary piston engine, the outlet nozzle of the combusion gas canbe opened in the exhausting stroke chamber. However, if the exhaustnozzle is opened merely on the center or side housing forming theexhausting stroke chamber, the nozzle will become loaded with sludge ina short time period similarly to the case of the secondary air supplynozzle as hereinbefore described.

SUMMARY OF THE INVENTION It is one object of the present invention toprovide a nozzlestructure adapted to open in an exhausting strokechamber of a rotary pistonengine which will not become loaded withsludge for a long period of time.

It is another object of the present invention to provide a nozzlestructure adapted to .open in an exhaust stroke chamber of a rotarypiston engine which may have means for preventing loading with sludge,and may be adapted to supply secondary air or remove part of the exhaustgas. p I

. It is a further object of the present invention to provide a nozzlestructure adapted to open in an exhaust stroke chamber of a rotarypiston engine which has means for removing sludge adhered thereto orpreventing an accumulation of sludge, by utilizing the pressuredifference between the adjacent chambers.

It is still another object of the present invention to provide a nozzlestructure adapted to open in an exhaust stroke chamber of a rotarypiston which prevents sludge from adhering thereto by providing at theopening of the nozzle a floating member moved by the pressure in thechamber.

BRIEF DESCRIPTION OF THE DRAWINGS These and'other objects, features andadvantages of the present invention will become apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a front elevational view in section of one example of a rotarypiston engine having an exhaust gas recirculating system with the nozzlestructure according to this invention;

FIG 2 is a front elevational view in section of one example of a rotarypiston engine having a secondary air supply system with the nozzlestructure according to this invention;

FIG. 3 is an enlarged sectional view of the nozzle portion opened in anexhausting stroke chamber of the rotary piston engine shown in FIG. 1 or2;

FIGS. 4 to 7 are expanded sectional views similar to FIG. 3 showingother embodiments of the present invention;

FIG.8 is a partial sectional view of a rotary piston engine in which anozzle is disposed at the side housing;

FIGS. 9 and 10 are sectional views taken along the lines IX-IX and XX,respectively in FIG. 8; FIGS. 11 to 13 are partialenlarged views ofother embodiments of nozzles for supplying secondary air on the innersurface of. the side housing which has a floating member; I

FIG. 14 is a view similar to FIG. 11 of the outlet nozzle for thecombustion gas; 7

FIGS. 15 to 17 are partial sectional views of the embodiments of thenozzle structure provided with a floating member moved by the pressureto the nozzle disposed at the center housing of the rotary pistonengine;

FIG. 18 is a front elevational view in section of an embodiment with thesecondary air supply device of the rotary piston engine having twocylinders where the nozzle structure has a floating member;

FIG. 19 is a side elevational view of the embodiment shown in FIG. 18;

FIG. 20 is an enlarged sectional view of the essential part of theembodiment shown in FIG. 18; and

FIG. 21 is a view similar to FIG. modification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, the samereference numerals illustrate the same parts.

In FIG. I, which shows one example of a rotary piston engine having anexhaust gas recirculating systemwith a nozzle structure according to thepresent invention, reference .numeral 1 illustrates a center housinghaving a trochoidal inner peripheral surface, 2 denotes side housingsdisposed at both sides of the center housing 1, 3 identifies a rotarypiston moving in planetary motion in a casing composed of thecenterhousing 1 and the side housings 2. The numerals 4 indicate apex sealsmounted to the respective apexes of the rotary piston in sliding contactwith the inner peripheral surface of the housing. The numeral 5 is anintake port opening in the housing such as, for example, in the side 20showing another housing 2, which is connected with a carburetor 7through an intake passage 6. The numeral 8 identifies an exhaust portprovided in the center housing. 9a is an outlet port or nozzle forcombustion gas opening on the inner surface of the housing such as, forexample, the center housing 1 forming an exhausting stroke chamber 10and connected through a conduit 11a to the carburetor 7. Thus, inoperation of the engine, the combustion gas in the exhaustingstrokechamber 10 is mixed through the nozzle 9a, the conduit 11a and thecarburetor 7 with the mixture in the intake gas passage 6 so as to berecirculated, thereby reducing the combustion efficiency of the mixtureso as to prevent NOx from being generated in large quantities.

FIG. 2 shows a rotary piston engine having a secondary air supply systeminstead of the exhaust gas recirculating system in the same type ofrotary piston engine as shown in FIG. 1. That is, a secondary air supplyport or nozzle 9b opens into the inner surface of the housing such as,for example, the center housing 1 forming the exhausting stroke chamber10, andv is connected to an air pump 12 through a conduit 11b. Thus, thesecondary air is supplied into the exhaustng stroke chamber 10 in orderto burn so as to remove unburned detrimental components such as CO, HC,etc. in the combustion gas. I

The nozzles opening in the exhausting stroke chamber, such as outletnozzle for the combustion gas of the exhaust gas recirculating systemshown in FIG. 1, or the secondary air supply nozzle of the-secondary airsupply system illustrated in FIG. 2 have means for preventing anaccumulation of sludge thereon.

The embodiments shown in FIGS. 3 to 7 serve to automatically remove thesludge accumulating on the nozzles by utilizing the pressure differencebetween the adjacent two operating chambers such as, for example,between the expanding stroke chamber and the exhausting stroke chamber,or between the exhausting stroke chamber and theintake stroke chamber.

In FIG. 3, which shows the nozzle portion opening in the exhaustingstroke chamber of the rotary piston engine shown in FIG. I or 2, arecess 14 of concave shape is provided on the seal sliding surface 13 ofthe center housing 1, and the nozzle 9 opens into the recess 14.Therefore, if the apex seal 4 of the piston 3 rotating in the directionas designated by the arrow reaches the recess 14 of the seal slidingsurface 13, the high pressure of the high pressure operating chamber Apasses through the gap formed around the apex seal 4 by the recess 14and discharges abruptly into the low pressure operating chamber B sothat any sludge tending to be accumulated near the opening of the nozzle9 is removed by the discharging forceof the high pressure gas.Accordingly, the loading of the nozzle opening with sludge may bepositively prevented.

FIG. 4 shows the nozzle portion wherein a sleeve 15 is mounted on theopen end of the nozzle 9 so as to project into the recess 14, and FIG. 5shows the nozzle portion wherein a sleeve 15 with a cover provided withflow ports 16 formed at the end of the peripheral wall thereof ismounted on the open nozzle end. Since the nozzles shown in FIGS. 4 and 5have the sleeves 15 projecting from the bottom surface of the recess 14,the loading of the openings with sludge due to the sliding of the apexseals 4 is more difficult than that shown in FIG 3.

The recess 14 may be selected of any suitable depth and shape such assquare or rectangular, and its disposition may also be in either thecenter housing or the side housings.

In the embodiment shown in FIG. 6, the opening of the secondary airsupply nozzle or outlet nozzle 9 for the combustion gas, opening on thesliding surface 13 of the center housing 1, is disposed in the lowpressure operating chamber such as, for example, exhausting strokechamber B. A high pressure inlet port 17 is formed in the adjacent highpressure operating chamber such as, for example, expanding strokechamber A, and is connected with the high pressure gas outlet 19 througha high pressure gas flow passage 18, and the outlet 19 is obliquelyconnected upwardly with the secondary air supply nozzle 9.

In FIG. 7, the high pressure gas passage 18 is formed by the method ofcutting to remove the unnecessary projecting portion after casting thebent pipe into the housing in advance instead of perforating the housingmechanically as shown in F IG. 6. I

Thus, with the rotation of the piston 3, when the apex seal 4 isdisposed between the high pressure inlet 17 and the high pressure outlet19, the high pressure operating chamber A and the low pressure operatingchamber B are connected through the high pressure gas flow passage 18.Therefore, the sludge tending to accumulate near the opening of thesecondary air supply nozzle or the outlet nozzle for the combustion gasis removed by the ejecting force of the high pressure gas, so as toprevent the loading of the nozzle opening with the sludge.

The disposition of the high pressure gas flow passage may be provided ineither the side housings or the center housing in the range forperforming the aforementioned operation.

The embodiments shown in FIGS. 8 to 10 are formed by disposing thenozzle structure shown in FIG. 5 on the side housing 2 so as to connectthe recess 14 with the exhaust port 8 through the groove 20. In thiscase, the groove 20 is so formed in width that the corner seals, sideseals or apex seals 4 may not fall therein. In

this embodiment, the recess 14 is provided on the sliding surface 21 ofthe side housing 2, the nozzle 9 opens into the recess 14, and therecess 14 is connected with the exhaust port 8 or in the neighborhood ofthe exhaust port 8 through the groove 20. Accordingly the supply" of thesecondary air or removal of the combustion gas may be continued until.the exhausting stroke is completed, and the accumulation of sludge isgreatly reduced so as to prevent the loading of the nozzle 9 with thesludge.

In the embodiment shown in FIGS. 11 to 13, the nozzle 9 for supplyingthe secondary air into the exhausting stroke chamber 10 is provided inthe side housing 2. A floating valve 22]) is movable provided in thenozzle end 9b connected with the secondary air conduit 11b so as not tomove into the operating chamber 10, and is so constructed as to open orclose the nozzle 9b by the difference between the secondary air pressurePa and the inner pressure Pb of the operating chamber 10.

In operation of the embodiment shown in FIGS.

11-13, the secondary air pressurized by the air pump and after thenozzle 9b, that is, the difference between the secondary air pressure Paof the conduit 11b and the inner pressure Pb in the operating chamber 10containing the nozzle 9b:

1. As shown in FIG. 11 on the condition of Pa Pb, the floating valve 22bis urged toward the operating chamber 10 side by the pressure of thesecondary air so that the nozzle 9b is opened and the secondary aircools the floating valve as it moves into the operating chamber.

2. On the condition of Pa Pa as shown in FIG. 12, since the stream ofthe secondary air is stopped, the floating valve 22b freely moves in thenozzle 9b to prevent the sludge from tending to'adhere onto the wallsurface or to remove the sludge adhered onto the wall surface.

3. On the condition of Pa Pb-as-shown in FIG. 13, the floating valve 22bis urged toward the conduit 11b by the pressure of the operating chamber10 to close the nozzle 9b and, accordingly, prevents the operating gasof high temperature and pressure from inversely flowing into the conduit11b.

In accordance with the foregoing description, the loading of the nozzle9b with sludge or the narrowing thereof is prevented by theprovision ofthe floating valve 22b to the nozzle 9b so as to stably supply thesecondary air so as to enable the reducing of the detrimental unburnedgas in the exhaust gas.

In the embodiment shown in FIG. 14, the same structure shown in FIGS. 11to 13 is applied to the exhaust gas outlet nozzle of the combustion gasof the exhaust gas recirculating system. In this case, when the pressurePa in the conduit lla connected with the carburetor is smaller than thepressure Pbin the operating chamber 10, it allows the combustion gas topass. When the pressure Pa is larger than the pressure Pb, it preventsthe reverse flow in the structure, and the floating member 22a movablyprovided in the nozzle 9a is the structure shown in FIG. 14.'Thus, theadhering of the sludge is prevented similarly to the case shown in FIGS.11 to 13.

FIGS. 15 to 17 show the embodiments wherein the nozzle 9 has a floatingmember .22 for floating in response to the differenceof the pressure'inthe conduit 11 and the pressure in the exhausting stroke chamber 10.

In the embodiment shown in FIG. 15, an opening 23 is provided on thesliding surface 13 of the center housing 1 forming the combustionchamber 10 during the exhausting stroke, a floating member 22 ofprojecting shape in section having a hole 24 through the center thereofis movably provided, and a ring 25 for preventing the floating member 22from discharging into the end of the opening 23 is engaged therewith.Thus, a passage 26 is formed between the outer wall of the floatingmember 22 and the inner wall of the opening 23. The floating member isso constructed as to be movable up and down and laterally in the passage26, at the same time the lower side of the opening 23 is connected tothe conduit 11. Numeral 27 shows a reinforcing wall.

According to the embodiment shown in FIG. 15, since the nozzle 9 isopened in the combustion chamber 10 during the exhausing stroke, thefloating member 22 vibrates upwardly and downwardly as well as laterallyby the pressure change of the pulsating exhausting gas, so that thesludge tending to accumulate in the hole 24,

opening 23 and passage 26 is mechanically removed by the vibration so asto positively prevent sludge from loading thereat.

In the embodiment shown in FIG. 16, as compared with that shown in FIG.15, the difference is such that a hole 24 is not formed through thefloating member 22, but when such structure is applied to the secondaryair supply system, the floating member 22 is depressed down by the highpressure gas until the exhaust port is opened so as to prevent thecombustion gas of high pressure from inversely flowing into thesecondary air supply passage. This action mechanically removes anyaccumulated sludge by the valve movement.

In the embodiment shown in FIG. 17, a slit 28 is formed on the uppersurface of the flange of the floating member 22 or on the lower surfaceof the ring 25 instead of the hole 24 in the embodiment shown in FIG.15. When this embodiment is applied to the secondary air supply system,the combustion gas of high pressure is prevented from inversely flowinginto the secondary air supply passage at the same time, even if thefloating member 22 is urged toward the ring 25 by the secondary airpressure, the secondary air. being continuously supplied through theslit 28 as its advantage. The disposition of the floating member may notonly be at the center housing, but be at the side housings within therange for performing the aforementioned operation.

The embodiments shown in FIGS. 18 to 21 are other examples of the casewherein the nozzle structure of this invention is applied toat'wocylinder rotary piston engine. These embodiments are particularlypreferable in the secondary air supply system and, accordingly, areshownand described with respect to the secondary air supply system. I

In the embodiments shown in FIGS. 18 to 20, the engines 30 and 31 aareintegrally assembled adjacent to the intermediate housing 32 as a commonside housing, and the respective pistons 33 and 34 are mounted on acommon eccentric shaft 35 in a phase difference of 180 degrees. When thepiston 33 of the engine 30 is disposed as designated by a solid line inFIG. 18, the piston 34 of the engine 31 is disposed as designated by adotted line in FIG. 18. In the engine 30, the mixture gas is introducedfrom air intake port 36 to air intake chamber 37, is compressed in thecompression chamber 38, and then the compressed mixture gas is ignitedby the ignition plug 39 to be burned, and in the operation chamber 40 ofthe state of the piston 33 as shown in the drawing, the lead side. ofthe flank 41 of the piston 33 is opened to the .exhasut port 42, and thecombustion gas is exhausted into the thermal reactor 43. whereupon, theengine 31, the trailing side of the flank 44 of the piston 34 is openedto the exhaust port 42. The secondary air is introduced from an air pump(not shown) through the secondary air inlet 46 having a check valve 45,and is poured into the respective operating chambers 40 and 50 of theengines 30 and 31, respectively, by the secondary air supply nozzles 48and 49, repectively, branched near the exhaust port 42 through thesecondary air pouring passage 47 formed in the intermediate housing 32.

As shown in FIG. 20, the secondary air supply nozzles 48 and 49 have anintegral floating member 53 having collars 51 and 52 at both endsthereof and passing through the intermediate housing 32 and floating inresponse to the pressure difference between the operating chambers ofboth cylinders in the secondary air supply nozzles 48 and 49 so as toeffectively remove the sludge by the movement of the floating member 53.As the alternative of the floating member 53 in FIG. 20, if a floatingmember 54 of the shape shown in FIG. 21 is used, the size of the hole ofthe intermediate housing 32 on the wall thereof becomes small so thatthe piston may smoothly rotate without engaging with the side sealing ofthe piston so as to remove the adhered sludge.

What is claimed is:

1. In a rotary piston engine comprising: a casing having a centerhousing and side housings disposed on repective sides of said centerhousing, a rotary piston rotatably mounted in said casing and having atleast one apex, an apex seal disposed in said piston apex, said apexseal slidably and sealably contacting said center housing inner surface,said casing and said rotary piston defining in order, intake,compression, combustion and exhaust chambers therebetween, an intakeport within I said casing opening up into said intake chamber forsupplying primary air to said intake chamber, an exhaust port withinsaid casing opening up into said exhaust chamber for exhaustingcombustion gas therefrom, and an auxiliary nozzle within said casingopening up into said exhaust chamber for supplying secondary air to saidexhaust chamber, or for removal of exhaust gas therefrom forrecirculation, the improvement comprising: means for preventing sludgeaccumulation about said auxiliary nozzle.

2. A rotary piston engine as set forth in claim 1, wherein said sludgeaccumulation prevention means is provided in the inner surface of saidcasing for releasing the high pressure gas from the high pressurechamber to the low pressure chamber of two adjacent chambers of theengine in response to the pressure difference between said chambers whenthe apex seal passes over said sludge accumulation prevention means,thereby removing the sludge accumulated on said nozzle owing to themovement of said apex seal.

3. A rotary piston engine as set forth in claim 2, wherein said meanscomprises a flow passage having an inlet and outlet provided in saidcasing and the open end of said nozzle is connected to said flowpassage.

4. A rotary piston engine as set forth in claim 3, wherein said outletof the flow passage is obliquely connected upwardly to the open end ofsaid nozzle.

5. A rotary piston engine as set forth in claim 3,

wherein said flow passage and said nozzle are provided in the centerhousing of said casing.

6. A rotary piston engine as set forth in claim 1, wherein said meanscomprises a floating member mounted within said nozzle and adapted tofloat longitudinally and laterally to remove sludge adhered to saidnozzle.

7. A rotary piston engine asset forth in claim 6, wherein said nozzle isconnected to an air source for supplying secondaryair through 'a conduitinto the exhausting stroke chamber, said floating member being throughthe conduit said floating member shutting off the communication of theconduit with the chamber when the pressure in said conduit is largerthan the pressure of said chamber, and connecting the conduit with thechamber when the pressure of said conduit is smaller than the pressureof said chamber.

9. A rotary piston engine as set forth in claim 6, wherein said floatingmember comprises a member of rivet shape engaged with said nozzle.

10. A rotary piston engine as set forth in claim 6, wherein saidfloating member is movably disposed at the open end of said nozzle, anda ring for preventing the floating member from being removed from thenozzle is provided at the end of said open end of said nozzle.

11. A rotary piston engine as set forth in claim 6, wherein said enginehas two center housings and an intermediate housing disposed betweensaid two center housings to form two adjacent cavities, an intake portand an exhaust port opening into the respective cavities, a conduitprovided in said intermediate housing, each nozzle being branched fromsaid conduit and opening at said intermediate housing into therespective cavities, and said floating member is composed of a singlemember in common with each nozzle.

12. A rotary piston engine as set forth in claim 11, wherein said eachnozzle forms a hole penetrating said intermediate housing in the axialdirection, and said floating member is movably mounted within said hole.

13. A rotary piston engine as set forth in claim 11, wherein saidconduit is connected to an air source, and said floating member hascollars at both ends thereof, said floating member being adapted tofloat longitudinally and laterally by the pressure in the exhaustingstroke chamber of the adjacent cavities.

14. A rotary piston engine as set forth in claim 10, wherein saidfloating member has a hole through the center thereof so as to connectthe conduit through the hole to the operating chamber.

15. A rotary piston engine as set forth in claim 10, wherein said nozzleis connected through the conduit to the secondary air supply source, anda floating member has a slit at the contacting surface with said ringfor allowing the secondary air to flow into the chamber when thepressure in the conduitis larger than the pres sure in the chamber.

16. A rotary piston engine as set forth in claim 2, wherein said meanscomprises a recess provided on the inner surface of said casing, and theopen end of said nozzle is disposed within said recess.

17. A rotary piston engine as set forth in claim 16, wherein said recessand said nozzle is provided in the center housing of said casing.

18. A rotary piston engine as set forth in claim 16, wherein said recessis provided in the side housing of said casing, and a groove forconnecting said recess to the exhaust port is provided.

19. A rotary piston engine as set forth in claim 16, wherein said nozzleincludes a sleeve at its open end to project into said recess.

20. A rotary piston engine as set forth in claim 19, wherein said nozzlecomprises a sleeve at 'its open end to project into said recess and saidsleeve is closed at the outer end thereof, and includes at least oneflow opening in its peripheral wall.

1. In a rotary piston engine comprising: a casing having a centerhousing and side housings disposed on repective sides of said centerhousing, a rotary piston rotatably mounted in said casing and having atleast one apex, an apex seal disposed in said piston apex, said apexseal slidably and sealably contacting said center housing inner surface,said casing and said rotary piston defining in order, intake,compression, combustion and exhaust chambers therebetween, an intakeport within said casing opening up into said intake chamber forsupplying primary air to said intake chamber, an exhaust port withinsaid casing opening up into said exhaust chamber for exhaustingcombustion gas therefrom, and an auxiliary nozzle within said casingopening up into said exhaust chamber for supplying secondary air to saidexhaust chamber, or for removal of exhaust gas therefrom forrecirculation, the improvement comprising: means for preventing sludgeaccumulation about said auxiliary nozzle.
 2. A rotary piston engine asset forth in claim 1, wherein said sludge accumulation prevention meansis provided in the inner surface of said casing for releasing the highpressure gas from the high pressure chamber to the low pressure chamberof two adjacent chambers of the engine in response to the pressuredifference between said chambers when the apex seal passes over saidsludge accumulation prevention means, thereby removing the sludgeaccumulated on said nozzle owing to the movement of said apex seal.
 3. Arotary piston engine as set forth in claim 2, wherein said meanscomprises a flow passage having an inlet and outlet provided in saidcasing and the open end of said nozzle is connected to said flowpassage.
 4. A rotary piston engine as set forth in claim 3, wherein saidoutlet of the flow passage is obliquely connected upwardly to the openend of said nozzle.
 5. A rotary piston engine as set forth in claim 3,wherein said flow passage and said nozzle are provided in the centerhousing of said casing.
 6. A rotary piston engine as set forth in claim1, wherein said means comprises a floating member mounted within saidnozzlE and adapted to float longitudinally and laterally to removesludge adhered to said nozzle.
 7. A rotary piston engine as set forth inclaim 6, wherein said nozzle is connected to an air source for supplyingsecondary air through a conduit into the exhausting stroke chamber, saidfloating member being adapted to connect the conduit with the chamberwhen the pressure in said conduit is larger than the pressure of saidchamber, and to shut off communication between the conduit and thechamber when the pressure in said conduit is smaller than the pressurein said chamber.
 8. A rotary piston engine as set forth in claim 6,wherein said nozzle is connected to an intake system to recirculatecombustion gas to the intake mixture through the conduit said floatingmember shutting off the communication of the conduit with the chamberwhen the pressure in said conduit is larger than the pressure of saidchamber, and connecting the conduit with the chamber when the pressureof said conduit is smaller than the pressure of said chamber.
 9. Arotary piston engine as set forth in claim 6, wherein said floatingmember comprises a member of rivet shape engaged with said nozzle.
 10. Arotary piston engine as set forth in claim 6, wherein said floatingmember is movably disposed at the open end of said nozzle, and a ringfor preventing the floating member from being removed from the nozzle isprovided at the end of said open end of said nozzle.
 11. A rotary pistonengine as set forth in claim 6, wherein said engine has two centerhousings and an intermediate housing disposed between said two centerhousings to form two adjacent cavities, an intake port and an exhaustport opening into the respective cavities, a conduit provided in saidintermediate housing, each nozzle being branched from said conduit andopening at said intermediate housing into the respective cavities, andsaid floating member is composed of a single member in common with eachnozzle.
 12. A rotary piston engine as set forth in claim 11, whereinsaid each nozzle forms a hole penetrating said intermediate housing inthe axial direction, and said floating member is movably mounted withinsaid hole.
 13. A rotary piston engine as set forth in claim 11, whereinsaid conduit is connected to an air source, and said floating member hascollars at both ends thereof, said floating member being adapted tofloat longitudinally and laterally by the pressure in the exhaustingstroke chamber of the adjacent cavities.
 14. A rotary piston engine asset forth in claim 10, wherein said floating member has a hole throughthe center thereof so as to connect the conduit through the hole to theoperating chamber.
 15. A rotary piston engine as set forth in claim 10,wherein said nozzle is connected through the conduit to the secondaryair supply source, and a floating member has a slit at the contactingsurface with said ring for allowing the secondary air to flow into thechamber when the pressure in the conduit is larger than the pressure inthe chamber.
 16. A rotary piston engine as set forth in claim 2, whereinsaid means comprises a recess provided on the inner surface of saidcasing, and the open end of said nozzle is disposed within said recess.17. A rotary piston engine as set forth in claim 16, wherein said recessand said nozzle is provided in the center housing of said casing.
 18. Arotary piston engine as set forth in claim 16, wherein said recess isprovided in the side housing of said casing, and a groove for connectingsaid recess to the exhaust port is provided.
 19. A rotary piston engineas set forth in claim 16, wherein said nozzle includes a sleeve at itsopen end to project into said recess.
 20. A rotary piston engine as setforth in claim 19, wherein said nozzle comprises a sleeve at its openend to project into said recess and said sleeve is closed at the outerend thereof, and includes at least one flow opening in its peripheralwall.